The distribution of content to mobile entities over a mobile communication network is of significant interest. Delivery of media, such as audio, pictures or video has widespread applicability. Technical implementations may be based on streaming technologies or on downloading. Streaming may be live streaming or on-demand. For illustration, media delivery to vehicles is regarded as being interesting. Examples include infotainment applications, the delivery of navigation-related information, or the delivery of traffic-related information. Car infotainment includes services such as media rendering systems (Compact Disc player, mp3 player, radio), backseat entertainment like video from disk or on demand, but also traffic and navigation information. Some or several of these services may be implemented such that the content is delivered to vehicles or other mobile entities over the internet. In the context of vehicle infotainment, this development is also referred to as “Connected Car Infotainment”. Audio streaming to mobile entities may be one of the first applications that will be used. A significant fraction of radio consumption happens in the car, and always being able to reach the favorite stations may be of interest to both users and service providers. At the same time, audio streaming has low driver distraction risk.
An increasing number of vehicles is expected to be equipped with both a cellular interface and at least one other communication interface. The other interfaces may include a Wi-Fi interface operative according to a standard of the IEEE 802.11 family. Certain protocols, such as IEEE 802.11p, have been standardized with special characteristics and requirements of Intelligent Transport Systems (ITS) in mind. Such protocols may be used for safety-related communication or other applications in communication between vehicles or other mobile entities.
However, even with very recent communication standards such as the 3GPP (Third Generation Partnership Project) specifications Rel. 10 (LTE Adv.), the number of mobile clients per radio cell which can be supported in content delivery over a mobile communication network may be fairly limited. For illustration, for a bit rate of 384 kb/s, approximately ten clients per radio cell may be supported with 3GPP Rel. 10. For greater bit rates, such as 1536 kb/s, the number may be even less, e.g. on the order of three. This similarly applies to other standards.
Further examples for the distribution of content to mobile entities include infotainment features, such as delivery of video or online gaming, to mobile phones or other handheld devices. When content is distributed to such devices, the radio access network of the mobile communication network may be prone to experiencing an overload situation when a large number of people located in the same area, such as a school yard, wishes to view the same movie at the same time. Similar overload situations in the radio access network may occur in any geographical area where many people are close to each other and share the same interests, which makes it likely that the same content must be distributed to them.
To increase the number of mobile entities to which content may be distributed, various approaches are conceivable. In one approach, Wi-Fi hotspots may be deployed for content delivery. A mobile entity which is in the coverage of a Wi-Fi hotspot may use the Wi-Fi connection and will be contacted through the Wi-Fi connection. If the Wi-Fi hotspot has a sufficiently great bandwidth, content may be delivered to a greater number of cars while attaining a good bit rate. However, such an approach may be very expansive and may require significant investments in infrastructure. For illustration, for hotspots deployed along a motorway, it may be estimated that approximately one access point every 500 meters would be needed.
In another approach, peer-to-peer (P2P) techniques on an uplink channel of the mobile communication network may be used. These channels may frequently be unused, for example for mobile entities which are vehicles or which are installed in vehicles. When several mobile entities request the same file, parts of the file which have already been downloaded by one of the mobile entities may be distributed to other mobile entities. A new mobile entity interested in the file does not need to use the download link, which allows a greater number of mobile entities to be served. An example for such an approach is described in L. Popova et al., “Cooperative Mobile-to-Mobile File Dissemination in Cellular Networks Within A Unified Radio Interface”, Computer Networks, vol. 52, no. 6, April 2008, pp. 1153-65. In such an approach which uses the uplink channel of the mobile communication network, the distribution happens only within the area of one Base Station (BS) or Radio Network Controller (RNC), without it being easily possible to capitalize on the proximity of other cars in other radio cells. This approach also requires the BS or RNC to be modified. Further, if the distance between mobile entities is less than ten meters, this approach may have interference problems. However, in situations such as traffic jams where techniques to relieve the radio network are of particular importance, such a minimum distance may be difficult to guarantee.